JP2004075531A - Siliceous filler and solidified material obtained through acidolysis of chrysotile and chrysotile-containing serpentine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a siliceous filler which has a high performance as a substitute for asbestos, a reduced biological influence and additional functions such as a moisture-conditioning function and high moisture absorption and release properties and provides a recycling means for wastes from asbestos-containing products by treating asbestos recovered from the products. <P>SOLUTION: The filler is obtained through acidolysis of chrysotile or chrysotile-containing serpentine and has a fibrous shape. Preferably, MgO is selectively dissolved through the acidolysis. Preferably, a chemical equivalent ratio of an acid used for the acidolysis to MgO (a basic component) contained in the serpentine or the asbestos is ≥2.3. The fibrous siliceous filler obtained through the acidolysis is mixed with water, molded and dried. <P>COPYRIGHT: (C)2004,JPO

Description

TECHNICAL FIELD The present invention relates to a siliceous filler and a solidified body obtained by acid-decomposing chrysotile and chrysotile-containing serpentine. The present invention relates to a siliceous filler and a solid having both functions and reduced effects on a living body.

Conventionally, chrysotile has been used as a raw material for cement-based building materials and as an admixture for adhesives and sealing agents. However, asbestos has been regulated and controlled for use as a substance that has an effect on living organisms, but its use has been determined to be banned in Japan.
In cement-based building materials, pulp, glass fiber, chemical fiber, and the like are used as an alternative to asbestos. Further, as an alternative to the admixture of the adhesive and the sealing agent, a mineral-based admixture is used.
Patent Document 1 discloses that carcinogenicity is reduced by coating the surface of an asbestos fiber with an organic polymer. However, while maintaining the strength of asbestos, coating the surface of asbestos fibers with an organic polymer impairs the water retention of asbestos and greatly reduces thixotropic properties.
JP-A-10-121376

In the case of natural products, asbestos substitute materials have limited production areas due to their required characteristics, and are expensive.In the case of synthetic products, prices are high, and they are widely used for interior building materials and interior finishing admixtures that require versatility. There is a problem that it is difficult, and in terms of performance, it is necessary to combine a plurality of substances in order to substitute for asbestos.
The present invention is intended not only to be used as an asbestos substitute, but also to provide a filler having a function and an added value more than that of the substitute by adding further functions to the substitute, thereby reducing biological effects. . Another object of the present invention is to provide asbestos that can be used as a means for recycling asbestos-containing product waste by treating asbestos recovered from asbestos-containing products.
Further, the present invention provides a versatile, low-cost, effective for use of recycled asbestos, a moisture control function, and a heat absorbing and discharging material for interior building materials and interior finishing admixtures useful for improving the indoor environment. An object of the present invention is to provide a siliceous filler having high wet performance and a solidified body using the filler.

The present inventors have continued intensive research to solve the above-mentioned problems, and the silica according to the present invention obtained by acid decomposition of chrysotile or chrysotile-containing serpentinite has a high humidity control function, and the effect on living organisms Was found to be significantly reduced, and the reason was ascertained as follows, and the present invention was completed.
a) Silica obtained by decomposing serpentine and asbestos retains its original structure (chrysotile structure) and has a hollow fiber structure.
b) The hollow diameter (pore diameter) is around 100 angstroms, which is the same level as the pores of diatom shale which is considered to have excellent moisture absorption / release performance.
c) Further, the specific surface area is increased to 200 to 300 m ² / g due to the desorption of MgO by the acid treatment, and in this respect, the specific surface area is equal to or more than that of diatom shale.
d) Asbestos (chrysotile) becomes amorphous due to acid decomposition.

That is, the present invention has solved the above-mentioned problems by the following means.
(1) A siliceous filler obtained by acid-decomposing chrysotile or chrysotile-containing serpentine and retaining a fiber shape.
(2) The siliceous filler according to (1), wherein MgO is selectively dissolved from chrysotile or chrysotile-containing serpentine by acid decomposition.
(3) The siliceous substance according to (2), wherein the amount of the acid used is 2.3 times or more in chemical equivalent ratio to MgO (base component) contained in the serpentine or asbestos. Filler.
(4) A siliceous solidified material obtained by mixing a silica filler having a fiber shape, obtained by acid-decomposing chrysotile or chrysotile-containing serpentine, with water, molding, and then drying to solidify.

Since the silica according to the present invention has high moisture absorption / desorption performance, it is useful as a high siliceous filler for interior building materials having a humidity control function and useful for improving the indoor environment, and has a reduced effect on living bodies. ing. Furthermore, it has thixotropic and reinforcing effects. In particular, with regard to the reduction of effects on the living body, cytotoxicity has been reduced, clastogenesis has been eliminated, subchronic lung injury has been reduced, and body fluid solubility has been increased, so problems such as chrysotile are eliminated. ing.
In addition, the silica according to the present invention can be easily obtained by acid treatment of chrysotile or chrysotile-containing serpentine which is abundant as a natural resource and widely distributed in Japan. When the acid treatment is performed, a versatile humidity-control interior material can be manufactured. Furthermore, since asbestos can be used as a raw material, it is also possible to use recycled asbestos obtained by collecting asbestos-containing building materials, so that resources can be effectively used. A solid can be obtained using this siliceous filler.

In the present invention, the raw material is serpentine, which is widely present in Japan as a natural resource, and silica obtained by subjecting the serpentine to acid treatment exhibits high moisture absorption / release properties and reduces the effect on living organisms. Thus, the present invention has been completed. In addition, it is possible to provide a recycling means for converting useful asbestos recovered from asbestos-containing building materials into non-asbestos and providing useful materials. Therefore, it is also possible to use recycled asbestos obtained by collecting asbestos-containing building materials.

In the present invention, a target siliceous filler is obtained by the following treatment.
(B) Crush serpentine or asbestos. The particle size is not particularly limited, but is preferably about 20 mesh or less in order to perform the acid treatment efficiently.
In addition, if a material that does not contain antigorite is selected from the serpentine as a raw material, the time required for acid treatment can be reduced. It is considered that the reason for this is that antigolite has high acid resistance and is difficult to decompose in acid, and it is considered that unlike anti-chrysotile, the antigolite does not have a hollow structure and does not contribute to moisture absorption and desorption. When antigorite is contained, the treatment can be sufficiently performed if the content is 10% or less.

(B) Pulverized serpentine or asbestos is put into an acid solution and decomposed with stirring.
The type of acid used is not particularly limited. The amount of acid used is required to be 2.3 times or more in chemical equivalent ratio with respect to the amount of MgO contained in serpentine or asbestos. In addition, the higher the temperature at the time of decomposition, the shorter the required time. At 100 ° C., if the treatment is performed for 1 hour or more, the purpose is achieved. Examples of the acid include hydrochloric acid, sulfuric acid, and nitric acid.

(C) After completion of the decomposition, the silica remaining as a residual residue is filtered off, washed with water, and dried to obtain the desired product.
The manufacturing process including the acid treatment for obtaining the above siliceous filler is summarized in FIG.

By using the obtained silica as a raw material for various interior wall materials, it becomes possible to produce interior materials having a humidity control function. In addition, although asbestos-containing serpentine and asbestos are used as raw materials, asbestos is completely modified by acid decomposition, so that there is no problem in safety.
(1) Silica fillers can be used as thixotropic fillers having a performance equal to or higher than that of chrysotile as admixtures for cement / resin because they retain the fiber form.
(2) By selectively dissolving MgO, it has a high specific surface area and has higher adsorptivity than diatomaceous rock, so it is an admixture excellent in humidity control function, deodorization function, and various harmful substance adsorption functions. Can be used. The specific surface area of diatomaceous earth is 120 m ² / g, whereas that of the fibrous silica of the present invention is about 220 m ² / g.

(3) The siliceous filler is mixed with water, molded, and dried to solidify to obtain a solid. As a molding method for this molding, for example, press molding, extrusion molding, or the like can be used. This solid does not require autoclave curing, etc., and is solidified only by molding and drying, so that energy-saving molding can be performed. Further, since the solid has the above-mentioned various properties (2), it can be used as an indoor environment improving material. It can be used as an air purification filter or the like. Further, since the strength of the solidified body is increased by firing, it can be used for a member requiring strength. Also, if impurities are completely removed during acid decomposition, a white solid is obtained, and if iron remains as an impurity, it is colored ocher (the color depth depends on the amount of iron remaining as impurities). You can get the body. Further, if a siliceous filler is blended into paper, paper (wallpaper) having the function (2) can be produced.
(4) Since the siliceous filler retains the fiber form and also has the reinforcing effect, it has the same reinforcing effect as glass fiber which is a chrysotile substitute fiber, and is used as a plastic reinforcing fiber. Available.

シ リ カ The siliceous filler of the present invention has a reduced effect on living bodies. To be more specific, there are test methods for examining the effects on living bodies, which can be confirmed by those test methods. For example, cytotoxicity can be determined by testing hamster cultured cells for the amount of lactate dehydrogenase released and the ability to form colonies. The same hamster culture cells are used to test for chromosomal abnormalities. Furthermore, the effect of the siliceous filler on the respiratory tract can be known by examining acute and subchronic lung injury. By examining the body fluid solubility, the effect of entering the body can be known. When the siliceous filler of the present invention was examined by these test methods, all showed reduced cytotoxicity and lost clastogenicity as compared to fillers from chrysotile or chrysotile-containing serpentine before acid decomposition. However, it was confirmed that subchronic lung injury was reduced and that body fluid solubility was increased.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

(Example 1) Example of acid treatment 100 g of serpentine powder was treated with 130 g of 98% sulfuric acid at 100 ° C for 2 hours to obtain 41 g of silica. Table 1 shows the processing conditions and the properties of the products.

(Example of humidity control building material)-Using sulfuric acid-
100 g of the silica obtained in the present invention was pulverized to a particle size of 100 mesh or less, a starch-based thickener was added in an amount of 0.5 wt% based on the total amount of silica, an appropriate amount of water was added, and the mixture was kneaded until it became a clay.
This raw material was extruded to form a plate-shaped molded body having a size of 100 mm thick × 100 mm wide × 150 mm long, and then fired at 700 ° C. for 1 hour to obtain a solidified body. Table 2 shows the performance of the obtained humidity control building materials.
FIG. 1 is a chart of an acid treatment step for producing a siliceous filler having high moisture absorption / release performance of the present invention from waste serpentine stone or asbestos-containing building material.

(Example 2)
Except that the acid for acid treatment was changed to hydrochloric acid, a solid obtained by the same method using silica obtained by the same method as in Example 1 was used, and the solidified product prepared by the same method was heated at a temperature of 20 ° C and a humidity of 90% for 24 hours. The change of the moisture absorption rate when repeating 24 hours at a humidity of 50% was measured. As comparative examples, diatom shale and sepiolite were similarly measured. Table 3 shows the measurement results.

(Example 3)
Using the silica obtained in Example 1 as a sample, (1) acid-decomposed silica thixotropic (thixotropic) was measured.
Mix at a sample / plasticizer (di-2-ethylhexyl phthalate) ratio of 0.4 (silica SP-07 has a large volume and therefore a sample / plasticizer ratio of 0.2) and use a rotary viscometer for 2 and 20 rotations. Was measured for viscosity. Thixotropic was determined by the following equation. All showed higher thixotropic properties than chrysotile.
Thixotropic (TI value) = 2 rpm viscosity / 20 rpm viscosity The test results are shown in Table 4 and FIG.

(Example 4)
Using the silica obtained in Example 1 as a sample, (2) the adsorption performance of fibrous silica was examined.
Each of fibrous silica and diatomaceous earth (5 g each) was placed in an odor bag (25 cm × 35 cm), heat-sealed, sealed with 3 liters of air, and added with ammonia to a gas concentration of about 500 ppm. This was left at room temperature, and after 10 minutes, the gas concentration in the bag was measured by a gas detector tube. Formaldehyde (about 20 ppm) was also tested in the same manner, and toluene (about 100 ppm) was similarly tested with measurement times of 10, 30, 60, 120, and 180 minutes. In addition, the same operation was performed without putting a sample, and this was set as a blank test. The test results for ammonia, formaldehyde, and toluene are shown in Tables 5, 6, and 7, respectively.

ア ン モ ニ ア Compared to the diatomaceous earth to be compared, ammonia is equivalent (below the detection limit), and formaldehyde and toluene are superior in the adsorption performance of the silica of the present invention.

(Example 5)
Using the silica obtained in Example 1 as a sample, (3) the moisture absorption / release performance of fibrous silica and diatomaceous earth was tested.
The sample was allowed to stand in a 20 ° C./50% atmosphere until a constant weight was reached. Next, the sample was left in an atmosphere of 20 ° C. and 90% for 24 hours, and the weight was measured. Thereafter, the sample was returned to the atmosphere of 20 ° C. and 50% and left for 24 hours and the weight was measured. This was repeated to observe the moisture absorption / release performance.
FIG. 3 is a graph showing the change in the moisture absorption / release performance. In the graph, the weight of the sample when the weight became constant was set to 100, and the weight change was expressed in%.
Compared to diatomaceous earth, fibrous silica has high moisture absorption / release performance.

(Example 6)
Using the fibrous silica obtained in Example 1 as a sample, a solidified acid-decomposed silica was obtained as follows.
A solid was obtained by kneading the mixture with the following composition and press molding.
[Blending] Fibrous silica: 100, organic fiber: 10, water: 50
[Solidified component] _{SiO 2 96%, Al 2 O} 3 3%, was Fe ₂ O ₃ 0.5%.
In order to determine the magnitude of the strength of the fired solid, the solid was fired at different firing temperatures, a destruction test was performed, and the magnitude of the load at the time of breaking was measured. Table 8 shows the measurement results. The higher the firing temperature, the greater the breaking strength.

(Example 7)
Papermaking was performed by mixing the fibrous silica obtained in Example 1 as a sample, and the moisture absorption / release performance and physical properties were confirmed.
[Specimen]
1) Humidity control function test and moisture absorption / desorption change test NBKP (softwood bleached kraft pulp) was mixed with silica SP-07 at the particle size and addition amount shown in Table 9 by a sheet machine to form a paper.
2) Physical property test A sheet machine was added to NBKP to add 20% of silica SP-07, whose particle size was not adjusted, and paper-making was performed.

[performance test]
1) Humidity control function test and moisture absorption / desorption change test (a) Humidity control function test 1. Leave at constant temperature at 20 ° C. and 50% atmosphere.
2. The weight of the test specimen when the constant weight is reached is set to 100.
3. Next, it is left in a 20 ° C./90% atmosphere for 24 hours, and its weight is measured.
4. After returning to an atmosphere of 20 ° C. and 50%, the weight is measured after standing for 24 hours. This is repeated, and the moisture absorption / release performance is observed.

The graph of FIG. 4 shows the humidity control function.
As a result of repeated moisture absorption and desorption, no performance deterioration due to the repeated moisture absorption and desorption was observed.
By adding the same amount of silica to the pulp content, the amount of moisture absorption is about 2.5 times, and the addition of twice the amount of silica is about 4 times, and the moisture absorption / desorption performance is greatly improved depending on the amount of addition.
The moisture absorption / release performance is hardly changed by the silica particle size.
(B) Moisture absorption / desorption change test 1. Dry at 105C for 24 hours to make it completely dry.
2. Place in an atmosphere of 20 ° C. and 90 RH%, and measure the weight change with time.
3. After 24 hours, the atmosphere is set to 20 ° C. and 50 RH%, and the weight change over time is measured similarly.
FIG. 5 is a graph showing the results of the moisture absorption / release change test. From this graph, it can be seen that the change in moisture absorption / desorption is almost flat after about 3 hours, and thereafter, the function of moisture absorption / desorption is almost eliminated, and it has a quick response and can respond to a sudden change in humidity.

2) Physical property test Table 10 shows the test results. According to this, although the bending strength is reduced, it is unnecessary performance for wallpaper. No problem was found in the physical performance as other paper.

[Test results]
1) Humidity control function test and moisture absorption / desorption change test The state of the paper after preparation is as shown in Table 11. (* When completely dry)

紙 Paper making with a sheet machine can be made without any problem. Raw material loss is 13% for pulp alone and 19% for silica alone. By adding the same amount of silica to the pulp, the thickness increases by about 50%. The color tone approaches the color of silica (gray) slightly.

(Example 8)
(6) The strength and the like in the case of plastic reinforcing fibers were measured.
Using fibrous silica and commercially available glass fiber, it was blended with PP to prepare a test body by injection molding, and the tensile strength and the like were measured. Table 12 shows the mixing ratio, and Table 13 shows the test results.

In the tensile test, the breaking strain is significantly lower than that of the blank or commercial glass fiber, but the elastic modulus is equivalent to that of commercial glass fiber, and the effect of increasing rigidity is equivalent to that of glass fiber.

[Tests on living organisms]
(Test Example 1) Cytotoxicity of siliceous filler Regarding cytotoxicity of siliceous filler, a test was performed on the release amount of lactate dehydrogenase (LDH) and colony forming ability (cell viability) using cultured Chinese hamster cells. . Compared to the positive control (chrysotile), the LDH at the 50 μg / ml dose level was about 1/3 and the colony forming ability was about 1:40 at the 50% cell viability level.

(Test Example 2) Chromosomal abnormality of siliceous filler The clastogenicity of the siliceous filler was examined using cultured Chinese hamster cells. The test was performed by a continuous test method (24 hours and 48 hours). The treatment concentration was set to five levels of 0.075, 0.15, 0.3, 0.45, and 0.6 mg / ml for both 24 hours and 48 hours. As a result of the test, the appearance rate of cells having a structural abnormality and the appearance rate of cells having a polyploid were both less than 5%, and it was judged that the fibrous silica gel had negative clastogenicity. The polyploid appearance rate of the positive control chrysotile at the level of 0.01 mg / ml was 25.7% and 23.1% at 24 hours and 48 hours, respectively.

(Test Example 3) Acute and subchronic lung injury of the siliceous filler As an effect on the respiratory organs of the siliceous filler, acute and subchronic lung injury caused by a single administration in the organ of a rat was evaluated by bronchoalveolar lavage (BAL). Investigations and respiratory effects compared to chrysotile were confirmed.
According to the cytological and biochemical analysis results of bronchoalveolar lavage fluid (BALF), Chrysotile, a positive control, showed an increase in neutrophils and eosinophils in the early stage of administration, an inflammation-related biochemical index (total protein (TP ) And lactate dehydrogenase (LDH) were increased and persistent, and alveolar macrophage (PAM) cytotoxicity / disintegration and advanced changes were observed. With the siliceous filler, the increase in the biochemical index at the early stage of administration was smaller than that of chrysotile, and the injury of PAM was also mild.

Histopathological examination showed that the positive control, chrysotile, showed bronchiolitis with germ cell metaplasia, recruitment / disintegration of PAM into the alveolar space, and granuloma and fibrosis in the bronchiole / alveolar tract. Severe lesions accompanied by hyperplasia were observed. On the other hand, siliceous fillers show lesions such as mild inflammation of bronchiole and alveolar tract, hyperplasia of bronchiolar epithelium, and recruitment of PAM to alveolar space. It was much less severe than chrysotile.

(Test Example 4) Body fluid solubility Chrysotile and siliceous filler were each dissolved in 0.5 and 1 liter of a biological approximation solution (gambling solution). In the test results, the chrysotile had low solubility in the gambling liquid, whereas the siliceous filler dissolved much. Moss Heidi (Ube Materials, basic magnesium sulfate whisker) is a synthetic fiber that has been confirmed to be non-carcinogenic, but has a lower solubility than the acid-decomposed silica (siliceous filler) of the present invention. Was. Table 14 shows the test results. In the test, the weight was measured after 6 hours and 24 hours, and the degree of solubility was evaluated based on the weight reduction ratio.

The present invention is used as an asbestos substitute, and by adding a function, it is possible to provide a filler having a performance and an added value in an alternative grade, and to reduce a biological effect. The recovered asbestos can be processed and used as a means of recycling asbestos-containing product waste.
Further, the present invention provides a versatile, low-cost, effective for use of recycled asbestos, a moisture control function, and a heat absorbing and discharging material for interior building materials and interior finishing admixtures useful for improving the indoor environment. It is possible to provide a siliceous filler having high wet performance.
Since the siliceous filler is solidified only by mixing with water, molding and drying, it does not require any special curing and can provide a solidified body useful for a humidity control function and an improvement in the indoor environment.

It is a process chart explaining the manufacturing method of the siliceous filler of the present invention. The test result regarding the thixotropic property of the acid-decomposed silica of the present invention is shown. The test result of the moisture absorption / release performance of the fibrous silica of this invention and diatomaceous earth is shown. The test result of the humidity control function of the fibrous silica of this invention is shown. The test result of the moisture absorption / release performance of the paper containing the fibrous silica of the present invention is shown.

Claims (4)

(4) A siliceous filler obtained by acid-decomposing chrysotile or chrysotile-containing serpentine and retaining a fiber shape. The siliceous filler according to claim 1, wherein MgO is selectively dissolved from chrysotile or chrysotile-containing serpentine by acid decomposition. (3) The siliceous filler according to (2), wherein the amount of the acid used is 2.3 times or more in chemical equivalent ratio to MgO (base component) contained in the serpentine or asbestos. (4) A siliceous solid body obtained by acid-decomposing chrysotile or chrysotile-containing serpentinite, obtained by mixing a siliceous filler having a fibrous shape with water, molding, and then drying and solidifying the siliceous filler.

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